In internal combustion engines for vehicles, a pressure sensor is provided in order to detect intake pipe pressure which serves as one indicator of how the engine is running.
More specifically, FIG. 4 shows a conventional internal combustion engine 108 disposed in an engine room 106 within a hood outline 104 of a vehicle 102. The engine 108 is provided with an intake manifold 112. The manifold 112 is equipped with a surge tank 110. A pressure sensor 120 is mounted on a vehicle-side panel 116 toward a dash panel 114 by means of a bracket 118. The pressure sensor 120 is connected to one end of a pressure introduction hose 122. The other end of the hose 122 is linked to a nipple 124. The nipple 124 is mounted on the surge tank 110 so that the intake pipe pressure of the tank 110 can be taken. Since vibrations on the side of the engine 108 differ from that on the vehicle body side, then respective portions of the pressure introduction hose 122, i.e. where the hose 122 is connected to the nipple 124 and pressure sensor 120, are loosened in order to prevent the hose 122 from being accidentally disconnected from the nipple 124 and/or the pressure sensor 120. In addition, the hose 122 is fitted with a clip (not shown) at an introduction portion of the hose 122 to this same end. Further, the routing of the hose 122 makes it difficult to position the nipple 124 at a distance greatly spaced away from the pressure sensor 120. To this end, components such as pipes are disposed between the nipple 124 and the pressure sensor 120.
Such examples of a pressure-detecting device for an internal combustion engine are disclosed in published Japanese Patent Applications No. 7-31094 and No. 3-121216. According to the former publication, the capacity of a piping system and/or a piping length are selected so as to be less than predetermined values, thereby preventing intrusion of liquid. According to the latter publication, an air reserve chamber is provided in the surge tank, and is connected to a pressure introduction hose.
In the conventional pressure-detecting devices, components such as the pressure introduction hose or pipe are used as cable routing. The hose, in this case, includes a passage therein having a small inner diameter. This causes an inconvenience in that: such a passage is liable to be clogged, either by foreign matter or by freezing; and, in particular, moisture readily resides in the pressure introduction hose at loose portions thereof, with a consequential increase in the likelihood of the hose freezing up at such loose portions.
Another inconvenience with the conventional devices is that such a structure makes it difficult to place the pressure sensor at the proper position for proper or optimum detection.